The invention generally relates to treatments for abnormal cell proliferation, particularly for treating epidermal disorders, and more particularly relates to a method of inhibiting abnormal cell growth with the use of certain corticotropin-releasing hormone (xe2x80x9cCRHxe2x80x9d) analogs. Inhibition of abnormal cell growth has therapeutic utility in conditions such as cancer and psoriasis.
Corticotropin-releasing hormone (CRH, also called CRF or corticoliberin) was first characterized as a 41-residue peptide isolated from ovine hypothalami by Vale et al. (1981). Subsequently, the sequence of human-CRH was deduced from cDNA studies and shown to be identical to rat-CRH, and then caprine, bovine, porcine, and white sucker fish CRH were characterized. The CRH of hoofed animals show considerable differences from man, but the pig and fish sequences differ from the human/rat sequence by only 2 out of 41 residues.
For some mysterious reason, peptides with homologous structures to mammalian CRH are found in cells of certain frog skins and in the urophysis of fish. In fact, the structure of sauvagine, the 40-amino acid peptide isolated from the skins of Phyllomedusa frogs, was reported several years before Vale""s description of ovine-CRH. The structure of sucker fish urotensin I was reported just months after the description of ovine-CRH and resulted from an independent line of inquiry by Lederis""s group in Canada. Although sauvagine and urotensin I release adrenocorticotropin (ACTH) from the pituitary, the functions of these peptides in the tree-frog (Phyllomedusa species that live in arid regions of South America) and in the sucker fish remain unknown.
In humans CRH regulates, via release of proopiomelanocortin, ACTH secretion from the anterior pituitary and has several direct actions on central and peripheral tissues. CRH has also been found to have direct anti-inflammatory properties. More recently, evidence has been provided that mammalian skin cells both produce CRH and express functional CRH receptors (Slominski et al., FEBS Lett., 374, pp. 113-116, 1995; Slominski et al., J. Clin. Endocrinol. Metab., 83, pp. 1020-1024, 1998; Slominski et al., Hum. Pathol., 30, pp. 208-215, 1999), although it was not known whether locally produced CRH had an additional role in the physiology of the skin, other than as a vasodilator and inhibitor of thermal injury-induced edema.
Some therapeutic methods and uses for CRH are described by inventors Wei and co-workers in U.S. Pat. No. 4,801,612, issued Jan. 31, 1989, titled xe2x80x9cMethod of Inhibiting Inflammatory Response,xe2x80x9d and U.S. Pat. No. 5,137,871, issued Apr. 26, 1994, titled xe2x80x9cTreatment to Reduce Edema for Brain and Musculature Injury.xe2x80x9d These patents describe the use of CRH to decrease the leakage of blood components into tissues produced by various adverse medical conditions, and thus to treat a patient for injury to or disease of the brain, central nervous system or musculature in which edema is a factor.
U.S. Pat. No. 5,869,450, issued Feb. 9, 1999, inventors Wei et al., describes CRH analogs in which the fifth amino acid from the N-terminus is D-Pro or in the case of urocortin or sauvagine where the fourth amino acid from the N-terminus is D-Pro or D-Ser. These analogs have an anti-inflammatory activity and a disassociated ACTH response.
Cyclic CRH agonists have recently been described by Rivier et al. (U.S. Pat. Nos. 5,844,074 and 5,824,771). These CRH analogs, modified by cyclization of residues 30-33 of CRH via a glutamic acid-lysine bridge, are more potent than native CRH in the release of ACTH and have lower molecular weight than native CRH. The elimination of residues 1-3 or 1-11 at the N-terminus of CRH has been shown to not alter biological activities or ACTH-release potency. (Kornreich et al., J. Med. Chem., 35, pp. 1870-1876, 1992; Koerber et al., J. Med. Chem., 41(25), pp. 5002-5011, 1998.)
Recently, Tjuvajev et al. (Tjuvajev, J., Kolesnikov, Y., Joshi, R., Sherinski, J., Koutcher, L., Zhou, Y., Matei, C., Koutcher, J., Kreek, M. J., and Blasberg, R. Anti-neoplastic properties of human corticotropin releasing factor: involvement of the nitric oxide pathway. In Vivo., 12, pp. 1-10, 1998. Department of Neurology, Memorial Sloan Kettering Cancer Center, New York, N.Y. 10021, USA) have introduced yet another novel mechanism for CRH in the form of anti-cancer action. Tjuvajev et al. (1998) reported a series of in vivo and in vitro studies that evaluated the anti-neoplastic potential of CRH in W256 rat mammary carcinoma. Using magnetic resonance imaging (MRI) and direct measurements of tumor and peritumoral brain water content they found that CRH treatment (100 micrograms/kg subcutaneously twice a day for 3 days) caused significant inhibition of growth of intracerebrally-injected W256 tumor cells. CRH also exhibited antiproliferative effects in in vitro cultures of W256 cells. The antiproliferative effects of CRH in W256 cells involve activation of nitric oxide synthase (NOS) and L-arginine-NO pathways. CRH activated the release of NO in W256 cells. The NO then became cytotoxic to the cancer cells.
Human trials of CRH for the treatment of peritumoral brain edema have been initiated and preliminary data indicated that CRH reduced brain edema associated with tumor metastases. However, the limiting factor on the use of CRH has been the known blood-pressure lowering property of CRH. CRH causes relaxation of smooth muscles surrounding blood vessels and causes vasodilation, resulting in a lowering of blood-pressure. The hypotension so produced is sufficiently dangerous to limit the dosages of CRH that can be administered to humans. If this dose-limiting toxicity is overcome by improved molecular design of CRH superfamily molecules, then it is conceivable that these analogs will have a higher therapeutic index and have utility via the anti-proliferative mechanism of action.
In one aspect of the present invention, a method of inhibiting abnormal cell proliferation in a patient diagnosed as being at risk of such condition is provided. In another aspect, practice of the invention provides a method of treating excessive epidermal proliferation. In yet another aspect of this invention, a kit is provided that is useful for treating a patient suffering from an abnormal cell proliferation conditions. The kit includes a pharmaceutically acceptable formulation of a corticotropin-releasing hormone (xe2x80x9cCRHxe2x80x9d) analog where the analog has a D-configuration amino acid residue at a particular location of the sequence, and the kit further includes instructional materials for therapeutic use of the pharmaceutically formulated peptide.
These inventive aspects relate to our having found that replacement of the glutamic acid residue at position 20 of CRH to a D-amino acid moiety creates a molecule that has minimal activity to lower blood pressure, but the molecule retains anti-proliferative actions in cell culture and inhibits experimental cancer growth in animals (mice and rats).
Thus, novel applications of [D-Xaa20]-substituted analogs of CRH, such as a preferred embodiment [D-Glu20], are herein described in which the ability to inhibit abnormal cell proliferation with reduced hypotension is utilized. The peptide analogs, such as are exemplified by [D-Glu20] CRH, have amino acid sequences of the CRH superfamily but wherein at least one amino acid residue at the 20 position has been replaced with a D-amino acid residue (however, peptides having 40 amino acid residues have the nineteenth such residue from the N-terminus modified by inclusion of a D-amino acid).
Among the novel uses of these peptide analogs are for the treatment of cancer and psoriasis, yet while avoiding the hypotensive properties of the normal CRH.